This invention relates to improved piston assemblies.
Prior art of possible relevance includes the following U.S. Pat. Nos.: 2,214,891 issued Sept. 17, 1940 to Schrom; 2,720,193 issued Oct. 11, 1955 to Maybach; 3,215,130 issued Nov. 2, 1965 to Maier; 3,323,503 issued June 6, 1967 to Grosshans et al; 3,463,057 issued Aug. 26, 1969 to Packard et al; 3,465,651 issued Sept. 9, 1969 to Tromel; 3,508,531 issued Apr. 28, 1970 to Squinto et al; and 3,738,231 issued June 12, 1973 to Zurner.
Over the years, many efforts have been made to provide a good piston assembly wherein the top compression ring is at a very high location immediately adjacent the crown. Such a location of the top compression ring minimizes the parasitic volume of a reciprocating mechanism in which such a piston is used, thereby improving performance. A high location also maximizes control over oil consumption and minimizes emissions of a noxious character.
Heretofore, notwithstanding the foregoing known advantages of such pistons, high top ring pistons have not been employed to the extent possible for any of a variety of reasons. In many designs, the top ring cannot be placed sufficiently high on the piston to minimize parasitic volume to the extent desired. Frequently, ring location has been lowered since it has been impossible to provide effective cooling of the top ring, which cooling is necessary to maintain a good lubricating oil film to prevent the shortening of the life of the ring.
In some cases, pistons with high top ring locations have not been satisfactory in that the groove receiving the ring is inadequately protected and is therefore prone to abnormal wear, shortening its life.
In other instances, the designs have been such that highly desirable, so-called "cocktail shaker cooling" for either or both the crown of the piston and a ring groove protection band has been impossible.